<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
       let name =  prompt('请你输入你的年龄')
       alert('哈哈哈哈，你今年' + name + '岁了！')
       </script>
</body>
</html>